Now if these circles were twisted round on the axis, so that the notch in one circle is applied opposite to the complete part of the other, the cam would act as a com plete circle, and the tooth of I would never drop into the notch of either, because the circumference of the other circle holds it up at the time. On the other hand, by placing the two notches opposite to each other, thc rol lers would be suffered to act upon the wire longer than is ever intended. Therefore between these two extremes, the limits of the notch may always be determined by trial, that the proper length of wire shall be protruded, one circle making the beginning, and the other the end of the notch in the cam. Both are fastened on the axis by clamp screws.
2. Tile centre screws, on which the whole of the pliers r r (Fig. 4,) are suspended, admit of adjusting them, so that their blades shall seize the wire by the middle, and make the ends of the staple equal when doubled.
3. The steel faces t and a, of the blade r of the pliers, can be removed, and any other substituted. This regu lates the distance between the legs and points of the card wire, or the length of its shank.
4. The screw in determines the degree of closure the side benders shall ham e ; and the square nut on the rod /, (which attaches to it the piece on which the cam ope rates,) determines the distance to which they will open. This is of consequence, for toe wire, if bent too sharply at once into the dotted position, (Fig. 2,) might be cut cr broken, instead of bent fairly.
5. The screw which fixes the lever 8 into the main axis, admits the lever to be set farther unit, and then it will give a greater degree of knee bend, or if nearer the axis will bend less. This is also influenced by the quan tity of motion the cam 9 gives to the pliers, which can be adjusted by sliding the curved piece I I tip or down the leer r, for which purpose its screws are fitted in grooves. This causes a more or less protuberant part of the rill're I I, to meet the Call' q. The screw 16, as be fore stated; adjusts the blade g of the pliers.
The wires being thus crooked, either by hand or by machinery, one to be stuck through the leathers, in whit.' holes are pricked for their reception. This was for ierly executed by the tedious process of pricking \vita a double awl, but now it is done by machines ; one kind adapted to the sheet cards, and the other for fillet ing. 'Fie Former consists of a square wooden frame, like a table wit.amt the top board. In this a square frame or carriage slides horizontally, and has cross bars, provided with jaw s to fasten, and screws to stretch the sheet of leather with a proper degree of tension. A cord is fastened to one end or the carriage, and passing over a pulley, has a weight attached to it, which always urges the carriage one war. It has a rack fastened to one side of it, the teeth of which are engaged by the worm of an endless screw, formed at the end or a long axis, placed parallel to the direction of the motion of the carriage, which is also parallel to the rack. The endless screw is prevented from running round, as it would do, by the weight drawing the carriage by a cylindrical brass wheel, the circumference of which has several circles traced upon it, each divided into a different number of divisions, and marked by small holes. A spring with a
tooth, or pin at the end, applies to these divisions, in the sante manner as the dividing plate of a wheel-cutting engine. Now, by lifting the spring tooth out of any divi sion, the weight operating upon the carriage draws it forwards, the teeth of the rack turning the endless screw about till another division comes to the tooth which drops into it, and holds it fast till the workman again relieves the spring catch. By this means the carriage and the leather is moved an equal quantity at every time, to measure the distance at which the rows of holes shall be pricked; and this measure can be altered at pleasure, by using a different circle of divisions. The holes are pierced by a double row of pickers, as long as the sheet of leather. They are small steel points fixed into a piece of iron, which is screwed to a strong frame, moving on two centre screws, forming an axis for it im mediately over the leather, and in a direction across that of toe motion of the carriage. On this axis the frame rises and falls in the manner of a book lid, when moved oy a long handle (lever) which is fastened to it. The row of points being fixed parallel to the axis, forms a double row of holes, when the lever is pressed down, in a di rection across the motion of the leather. A proper bed is prepared beneath the leather, just where the points act, to support the sheet while it is pierced. This ma t-111)t is used as follows : A sheet of leather is prepared by rubbing the grain side with soap, and sizing over the lb sh side. It is then fixed to the two ( ross bars of the carriage, by the jaws vvhidi bite its edge East; and the two scrvv,s first mentioned, the sheet is strain d very tight. All this time the lever and prif ker frame is torn cd up out of the way; and the end of the lever In Mg suspended from the ceiling, but the leather being fixed, the workman adjusts the carriage to the proper point of commencement, and then strikes down the end of the lever, pricking one double row of holes across the whole length of the sheet; he then lifts up the lever, and, tak ing the spring catch of the dividing cylinder in the other hand, lifts its point out of a division, suffering the car riage to move till the next division Collies to the catch ; then lie strikes down the lever, and pricks another dou ble row, and at the same time that he lifts it up again he suffers another division to pass by ; and in this manner the operation proceeds with great rapidity, till the whole sheet is finished. The pricker, it should he observed, is provided with a double row of points, and pierces two rows at once, that the points of one may fall opposite the spaces of the next row ; a condition which it would be difficult to effect by other means than piercing two at once.